CSCI 454/554 Computer and Network Security. Instructor: Dr. Kun Sun

Transcription

1 CSCI 454/554 Computer and Network Security Instructor: Dr. Kun Sun

2 About Instructor Dr. Kun Sun, Assistant Professor of Computer Science Phone: (757) Office: McGrothlin-Street Hall, 105 Office hours 2:00pm-3:15pm MW, or by appointment (send me ) 2

3 About TA Wenting Tan Office: : McGrothlin-Street Hall, 107-A Office Hour: by appointment (send ) 3

4 Course Objectives Understanding of basic issues, concepts, principles, and mechanisms in computer and network security. Basic security concepts Cryptography Authentication Kerberos IPsec and Internet key management SSL/TLS Firewall Be able to determine appropriate mechanisms for protecting networked systems. 4

5 Course Outline Basic Security Concepts Confidentiality, integrity, availability Security policies, security mechanisms, security assurance Cryptography Basic number theory Secret key cryptosystems Public key cryptosystems Hash function Key management 5

6 Course Outline (Cont d) Identification and Authentication Basic concepts of identification and authentication User authentication Authentication protocols 6

7 Course Outline (Cont d) Network and Distributed Systems Security Public Key Infrastructure (PKI) Kerberos IPsec IPsec key management SSL/TLS Firewalls 7

8 Course Outline (Cont d) Miscellaneous topics Evaluation of secure information systems Mobile security Cloud security Malicious software Security management 8

9 Project Research paper Survey paper Term Project See the class website for detailed requirement You are expected to explore issues beyond what s included in lectures by yourselves 9

10 What s Left Out? Hacking System configuration, O.S. internals Political, legal, regulatory Financial, economics Social, psychological, human factors Morals, ethics Operational, business procedures, logistics 10

11 Prerequisites Programming experience in Java and C is required Knowledge in data communication and networking CSCI

12 Required textbook Textbook Charlie Kaufman, Radia Perlman, and Mike Speciner, Network Security: Private Communication in a Public World, 2nd Edition, Prentice Hall, ISBN-13: , ISBN-10:

13 WWW page: On-line Resources csci454-s15/index.html For course materials, e.g., lecture slides, homework files, project, tools, etc. Will be updated frequently. So check frequently. 13

14 Grading CSCI 454 Homework assignments 25% Term project: 10% Midterm exam: 30% Final exam: 35% CSCI 554 Homework assignments 20% Term project: 30% Midterm exam: 20% Final exam: 30% Note: you must use text editor (e.g. MS Word, latex) to complete your homework and project. Handwritten submissions are not accepted. 14

15 Policies on late assignments Homework and project deadlines will be hard. Late homework will be accepted with a 10% reduction in grade for each day they are late by. Once a homework assignment is discussed in class, submissions will no longer be accepted. 15

16 Policies on Absences and Makeup You may be excused from an exam only with a university approved condition, with proof. For example, if you cannot take an exam because of a sickness, we will need a doctor's note. Events such as going on a business trip or attending a brother's wedding are not an acceptable excuse for not taking an exam at its scheduled time and place. You will have one chance to take a makeup exam if your absence is excused. There will be no makeup for homework assignments. 16

17 Academic Integrity The university, college, and department policies against academic dishonesty will be strictly enforced. Honor code Students are required to follow William and Mary's Honor System, as described in the student handbook. 17

18 Check the website for details! 18

19 CSCI 454/554 Computer and Network Security Topic #1. Basic Security Concepts

20 Why This Course? Symantec Internet Security Threat Report

21 Why This Course? Increased volume of security incidents Security threats Malware: Virus, worm, spyware Spam Botnet DDoS attacks Phishing Cross-site scripting (XSS) 21

22 Contributing Factors Lack of awareness of threats and risks of information systems Security measures are often not considered until an Enterprise has been penetrated by malicious users The situation is getting better, but (Historical) Reluctance to invest in security mechanisms The situation is improving Example: Windows 95! Windows 2000! Windows XP! Windows Vista! Windows 7! Windows 8 But there exists legacy software Wide-open network policies Many Internet sites allow wide-open Internet access 22

23 Contributing Factors (Cont d) Lack of security in TCP/IP protocol suite Most TCP/IP protocols not built with security in mind Work is actively progressing within the Internet Engineering Task Force (IETF) Complexity of security management and administration Security is not just encryption and authentication Software vulnerabilities Example: buffer overflow vulnerabilities We need techniques and tools to better software security Hacker skills keep improving Cyber warfare 23

24 Security Objectives Confidentiality (Secrecy) Integrity Availability (Denial of Service) 24

25 Security Objectives (CIA) Confidentiality Prevent/detect/deter improper disclosure of information Integrity Prevent/detect/deter improper modification of information Availability Prevent/detect/deter improper denial of access to services provided by the system These objectives have different specific interpretations in different contexts 25

26 Commercial Example Confidentiality An employee should not come to know the salary of his manager Integrity An employee should not be able to modify the employee's own salary Availability Paychecks should be printed on time as stipulated by law 26

27 Military Example Confidentiality The target coordinates of a missile should not be improperly disclosed Integrity The target coordinates of a missile should not be improperly modified Availability When the proper command is issued the missile should fire 27

28 A Fourth Objective Securing computing resources Prevent/ detect/deter improper use of computing resources including Hardware Resources Software resources Data resources Network resources 28

29 Achieving Security Security policy What? Security mechanism How? Security assurance How well? 29

30 Security Policy Organizational Policy Automated Information System Policy 30

31 Compusec + Comsec = Infosec Compsec Security Comsec Computers Communications Infosec 31

32 Security Mechanisms In general three types Prevention Example: Access control Detection Example: Auditing and intrusion detection Tolerance Example: Byzantine agreement Good prevention and detection both require good authentication as a foundation 32

33 Security Mechanisms (Cont d) Prevention is more fundamental Detection seeks to prevent by threat of punitive action Detection requires that the audit trail be protected from alteration Sometime detection is the only option, e.g., Accountability in proper use of authorized privileges Modification of messages in a network Security functions are typically made available to users as a set of security services Cryptography underlies (almost) all security mechanisms 33

34 Security Services Security functions are typically made available to users as a set of security services through APIs or integrated interfaces Confidentiality: protection of any information from being exposed to unintended entities. Information content. Parties involved. Where they are, how they communicate, how often, etc. Authentication: assurance that an entity of concern or the origin of a communication is authentic - it s what it claims to be or from Integrity: assurance that the information has not been tampered with 34

35 Security Services (Cont d) Non-repudiation: offer of evidence that a party is indeed the sender or a receiver of certain information Access control: facilities to determine and enforce who is allowed access to what resources, hosts, software, network connections Monitor & response: facilities for monitoring security attacks, generating indications, surviving (tolerating) and recovering from attacks 35

36 Security Assurance How well your security mechanisms guarantee your security policy Everyone wants high assurance High assurance implies high cost May not be possible Trade-off is needed 36

37 Security by Obscurity Security by obscurity If we hide the inner workings of a system it will be secure Less and less applicable in the emerging world of vendor-independent open standards Less and less applicable in a world of widespread computer knowledge and expertise 37

38 Security by Legislation Security by legislation says that if we instruct our users on how to behave we can secure our systems For example Users should not share passwords Users should not write down passwords Users should not type in their password when someone is looking over their shoulder User awareness and cooperation is important, but cannot be the principal focus for achieving security 38

39 Security Tradeoffs Security Functionality COST Ease of Use 39

40 Threat-Vulnerability-Risk Threats Possible attacks on the system Vulnerabilities Weaknesses that may be exploited to cause loss or harm Risk A measure of the possibility of security breaches and severity of the ensuing damage Requires assessment of threats and vulnerabilities 40

41 Threat Model and Attack Model Threat model and attack model need to be clarified before any security mechanism is developed Threat model Assumptions about potential attackers Describes the attacker s capabilities Attack model Assumptions about the attacks Describe how attacks are launched 41

42 Risk Management Risk analysis NIST Common Vulnerability Scoring System (CVSS) Mathematical formulae and computer models can be developed, but the parameters are difficult to estimate. Risk reduction Attack surface, Attack graph Risk acceptance Certification Technical evaluation of a system's security features with respect to how well they meet a set of specified security requirements Accreditation The management action of approving an automated system, perhaps with prescribed administrative safeguards, for use in a particular environment 42